Epidermal Growth Factor in Mouse Ocular Tissue: Effects of Thyroxine and Exogenous Epidermal Growth Factor

Abstract

ABSTRACT. Using a specific and sensitive epidermal growth factor (EGF) radioimmunoassay, we identified radioimmunoasayable EGF both in developing and adult mouse ocular tissues. In neonatal animals ocular EGF concentrations increase during the first 4-9 days and then decline between 9 and 15 days. Thyroxine (T4) administration (0.4 pg/g body weightlday from day 0) increased local EGF concentrations in eye and skin of 7-day-old neonatal mouse pups. However, this treatment did not affect submandibular gland EGF concentrations during the 1st wk of life. Both EGF and T4 are known to accelerate eye opening in the neonatal mouse. Exogenous EGF administration (2 pg/g body weightlday) during the first 8 days of life elicited precocious eyelid opening as expected but did not alter the serum T4 concentration, suggesting that EGF does not mediate eye opening by T4 dependent mechanism(~). Tissue EGF measurements revealed that the exogenous EGF was localized in skin and eye; however, other tissues including lung, liver, heart and submandibular gland also contained exogenous EGF. Kidney-EGF concentrations did not rise while brain-EGF levels were significantly decreased after exogenous EGF, suggesting that different EGF uptake and regulatory mechanism(s) exist in different tissues during the neonatal period. T4 administration (0.4 pg/g body weightlday) for 10 days to adult mice also increased ocular-EGF concentrations. However, this increase was abolished by sialoadenectomy, suggesting in contrast to the newborn, that submandibular gland is an important source of ocular-EGF in adult mice. These studies indicate that ocular EGF in the mouse is thyroxine responsive only during the neonatal period. (Pediatr Res 19: 315-319,1985) Abbreviations T4, thyroxine EGF, epidermal growth factor BW, body weight SMG, submandibular glands RIA, radioimmunoassay T3, triiodothyronine

Epidermal Growth Factor in Neonatal Mouse Urine: Maturative Effect of Thyroxine

“…dose and timing of the urine EGF response to T4 (from birth to The effect of T4 on urine EGF appears to be highly specific in 6 days of life) are similar to these aspects of the T4 effect on EGF that the hormone injection did not alter urine urea nitrogen in skin (22) and ocular tissue of newborn mice (24). These results indicate that both tissue and body fluid EGF levels are subject to hormone modulation during the perinatal stage.…”

Neonatal Hyperthyroidism in Mice Has Different Effects on Epidermal Growth Factor Levels in Submandibular Gland, Urine, and Blood

“…There is some evidence that the accelerating effect of T4 on incisor eruption and eyelid opening may be mediated by EGF. A similar acceleration is produced by exogenous EGF (I), and T4 treatment increases the EGF content of neonatal mouse ocular tissue (17). In the present study, involving a brief period of neonatal hyperthyroxinemia followed by a period of hypothyroxinemia, eyelid and tooth development were accelerated, indicating that the brief period of hyperthyroxinemia triggers these tissue responses which are then unaltered despite a subsequent period of hypothyroxinemia.…”

Epidermal growth factor acts as a corticotropin-releasing factor in chronically catheterized fetal lambs.

“…EGF production in mouse SMG is thyroxine and testosterone responsive and urine EGF production and kidney EGF concentrations are thyroxine responsive in the mouse (10)(11)(12). EGF concentrations in several other tissues including liver, skin, and eye also are thyroxine responsive (13,14) as is EGF receptor binding in skin and liver (15,16). Finally, EGF has been shown to evoke hormone secretion from cultured anterior pituitary cells (17)(18)(19), and a recent paper reports that EGF augments ACTH release in vivo in adult sheep (20).…”

“…Materials. EGF was purified to homogeneity from adult Swiss Webster mice as reported previously (14,22). The final product migrated as a single band by polyacrylamide gel electrophoresis and had an apparent molecular mass approximating 6,000 D. oCRF, synthesized using solid phase techniques, was purchased commercially (Bachem Co., Torrance, CA) and used for injection and for development of the radioimmunoassay.…”